TBN on cooldown. stagger the remaining cooldowns. Don't forget stun is a form of damage mitigation as well, weave that in on stuff that hits hard.

TBN is a very powerful tool. The feedback I'm getting from my FC's healers, is that DRK is the easiest to heal in dungeon wall-to-walls. The one thing to consider with TBN is if you're running with a WHM and they pop swift on holy. it can deny you a pop. No longer a concern after diminishing returns though.